Jump to content

True or Magnetic


Miller Family
Followers 0

Recommended Posts

More accurate does not really apply.

You will get preferences on both side, and both work.

But.. consider this.

1)They call it True North for a reason.

2)your GPS "thinks" in true and make an adjustment to display magnetic

3) many roads are laid out in True

4) when using a magnetic compass with you GPS it is easy to adjust the compass declination either with an adjustable compass or simply by placing the needle on 20 degrees to the right of "N" if your declination is 20 degrees East (or likewise whatever your declination is)

Link to comment

Short answer: It doesn't matter in the least.

 

Long answer. If you are using a paper map without a compass, use True North. If you are using a magnetic compass without a map, you get a better match using magnetic north. If you are using both map and compass, you either need to know the magnetic variation (declination) and correct the compass or use True North and keep the compass in your pocket. If you are using neither map or compass, it doesn't matter.

 

Most cachers use True North and leave it there.

Link to comment

The Magellan units' compass will only work if you are moving at a certain speed. This has nothing to do with which north setting you have. The explorist series, i believe, gets it compass heading from the satellites so it is not a true electronic compass. Because of this you must be moving at least 2mph (i think thats the right speed) for it to be accurate.

Link to comment

More accurate does not really apply.

You will get preferences on both side, and both work.

But.. consider this.

1)They call it True North for a reason.

2)your GPS "thinks" in true and make an adjustment to display magnetic

3) many roads are laid out in True

4) when using a magnetic compass with you GPS it is easy to adjust the compass declination either with an adjustable compass or simply by placing the needle on 20 degrees to the right of "N" if your declination is 20 degrees East (or likewise whatever your declination is)

I agree, for caching it doesn't make much difference and there are good reasons to use true (like your #3). But when I got into letterboxing I found that many clues use magnetic bearings rather than true (probably so you can use any cheapo, non-declination-adjustable compass). That messed me up for awhile and I found that I was no good at doing what you suggest in #4, so switched my 60CSx to magnetic. Then I found the compass in my 60CSx is so bad it doesn't matter anyway, switched it back, and pulled out my old Suunto. It's fun using a real compass again anyway! :anicute:

Link to comment

if you calibrate your compass on your 60csx i think your results would be better with it.

Nope. I love the 60CSx - its great reception even under heavy tree cover; its nearly-unlimited POIs with custom icons - but the (magnetic) compass is junk. Even after calibration it is jumpy and wildly inaccurate. Drive around a bit and it needs calibration again. This is common on these units. For cache-seeking, I get much better results turning the compass off and relying solely on GPS. For letterboxing or map work, I use a real compass.

Link to comment

I think those of us who have actually truly used a magnetic compass to any degree (pardon the pun!!) can really appreciate how innacurate the electronic compasses in gps are. People who worked with forestry or wildlife, or ran survey lines and that kind of work are the people who know how to use a magnetic compass, and know how accurate they can be. I know there will be arguments here, but if you haven't used a magnetic compass to it's potential then you have no right to argue. If you have, then fire away!!

Link to comment

3) many roads are laid out in True

 

Well... that's a really tough argument.

Honestly, does it really matter if the road is laid out in true or magnetic?

 

For me, always magnetic - my compass indicates the magnetic north always, so why bother and correct for declination when the GPS can do it?

Link to comment

 

Honestly, does it really matter if the road is laid out in true or magnetic?

 

 

Well, yes and no. If it was laid out in magnetic, and declination was NOT accounted for, then YES...BIGTIME. If declination was accounted for, then no.

 

Do many of you know that the difference in a compass reading from the east coast of Canadato the west coast of Canada has a magnetic variation of over 40 degrees. varying from (these are approximate numbers) 26 degrees west where i live to somewhere around 20 degrees east on the west coast. This would mean that if i had my magnetic compass adjusted for magnetic north here on the east coast and travelled to the west coast, that my compass would point me OFF COURSE by more than 45 degrees. Magnetic variation is quite significant. And using it without knowledge of it's implications can be dangerous if nothing else. Using it WITH the proper knowledge, then it is quite fine.

 

And these numbers are not consistent either. Magnetic North changes location over time. Perhaps more than you think. And to make matters worse, the rate of change is NOT constant!

 

Just a few pieces of trivia:

The magnetic pole has moved about 700 miles into the Canadian arctic over the last 10 years.

Scientists are predicting that the magnetic pole is moving at such a fast rate that in the next 50 years it will move OUT of Canada and into Siberia!

At very high latitudes the change in magnetic variation can be as much as 1 degree per kilometer!!

 

So yes, if you are using magnetic north, you should at least be aware that it is NOT always in the same place. Don't matter much on a GPS, but with a handcompass you better know what you're doing.

Link to comment

Dont forget Grid North which "should" be used when using UTM maps :blink:

 

Yep. A lot of people using UTM maps actually set their gps to UTM. It's easier to read UTM than lat/long from a paper map like Canadian Topo maps. Most UTM maps can also be used with true north though, as the edges of the maps line up exactly with true north. There is usually a legend showin true north aligning with the map edge, and lines showing grid north variation and magnetic north variation. Again, only magnetic north varies.

Edited by GreatCanadian
Link to comment

My declination here near Seattle is 18.5East.

Nice thing about a GPS is that you don't have to mess with magnetic variations at all. The GPS is not based on the Earths magnetic field, but rather on satellite orbits, and thus you always have a true True North with out any need for adjustments. It is when you switch the gps to magnetic that the unit offsets that reading based on your location. If you use a electronic compass (I have one that stays in my drawer, and I take my regular compass) then that is based on the magnetic field as I assume is also the one in the cxS.

 

If you want your declination for a new area just switch you GPS to "magnetic" and it shows your declination value, so you can use it to adjust your compass to read True.

 

Personal choice, but I always use True in my gps, and simply lay the needle on the compass over the proper declination to give a true reading. Easy, accurate.

 

Here is the daily movement on the magnetic north pole:

 

nmpoval2001d_e.gif

 

World Declination! (fist in the air):

Declination.jpg

Edited by EraSeek
Link to comment

 

Honestly, does it really matter if the road is laid out in true or magnetic?

 

 

Well, yes and no. If it was laid out in magnetic, and declination was NOT accounted for, then YES...BIGTIME. If declination was accounted for, then no.

 

I understand the importance of magnetic declination - where i live it's about 11 degrees.

However, what I wanted to say is that when I'm on the road, the road leads me to destination. I don't need to know whether it it goes towards the true north or magnetic north - I have a road map in my car anyway. The roads have never been built like a straight line between two points. This thing with 'Take Hwy xxx North' is only in North America. In Europe, people say 'Take Hwy xxx towards <City>'. It doeans't matter whether you drive Norht or East or... whatever.

Then, taking a winding road... Does it still matter whether your GPS is set up to Magnetic North or True North? I don't think so.

 

What matters the most is when you are hiking and using a topo map - ten for sure you need to know where is what. That's why I prefer magnetic to true because I can alway take a bearing with by compass and project a waypoint in my GPS without the need to convert from magnetic to true. That's why I consider that magnetic is more important than true because, after all, all compasses point to magnetic north (well... at least those used in the northern hemisphere).

Link to comment

 

The magnetic pole has moved about 700 miles into the Canadian arctic over the last 10 years.

Scientists are predicting that the magnetic pole is moving at such a fast rate that in the next 50 years it will move OUT of Canada and into Siberia!

 

 

Just so long as it doesn't affect the taste of the beer :laughing:

 

A small diversion: I had an engineering professor in the mid '80s who insisted that slide rules were faster than digital calculators, especially with roots and logs. He would wager $1 bets on races to solve complex arithmetic - his slide rule vs a calculator. He usually won. As far as I know, none of his students gave up their calculators for a slide rule (or even learned to use one for that matter).

 

Those of us who are trained in orienteering probably have a need for that training and we will always choose a magnetic compass. If you are headed off grid - into Great Canada, the Great West, or out to sea - then precision and competence are essential.

 

For those of us seeking tupperware in a State or Provincial park ... the GPS compass and a good dose of common sense will get the job done. At that point, the choice of magnetic or true becomes a bit esoteric. My thoughts.

 

Have Fun - Be Safe!

Link to comment

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

Loading...
Followers 0
×
×
  • Create New...